Method of manufacturing a tubular member

Abstract

A method of manufacturing a tubular component including rough machining the exterior surface of a solid billet 1 to reduce the size thereof and form two flanges. An axial blind bore 6 is then machined in the billet 1 , after which a probing operation is carried out on the interior surface of the bore 6 in order to check the concentricity. A straightening operation is then performed on the billet in order to reverse any curvature along the longitudinal axis. A further machining operation is then performed on the outside to reduce the wall thickness of the bore before measuring the wall thickness of the bore 6 around the circumference of the billet 1 at least at two different axial positions. The billet 1 is then checked again and a final machining operation is then performed in order to form any ports and upstands which are required.

What is claimed is: 
     
       1. A method of manufacturing a tubular component comprising the steps of:
 (a) rough machining an exterior surface of a solid billet of material to reduce the size thereof and form at least a first radially extending flange and a second radially extending flange on the exterior of the billet, said flanges being centered on and axially spaced along a longitudinal axis of the billet; 
 (b) machining a bore which extending axially in the billet; 
 (c) performing a first probing operation on the interior surface of the bore in order to check a concentricity of the interior surface about a flange axis which extends longitudinally between the centers of the first and second flange by measuring any variation in the distance of the internal surface from the said flange axis around the inner circumference of the bore at a first point within said first flange, a second point within said second flange, and at least a third point which is longitudinally spaced between said first and second flanges; 
 (d) performing a first straightening operation on the billet in order to reverse any curvature along the longitudinal axis outside of allowed tolerance for the component identified in the billet by measurement of variations in the distance of the inner surface of the bore from the flange axis around the inner circumference of the bore at any of a measurement points during the first probing step which are outside of allowance tolerance for the component; 
 (e) performing a further machining operation on the exterior surface of the billet to reduce a wall thickness of the bore; 
 (f) measuring the wall thickness of the bore around the circumference of the billet at least at two different axial positions along the billet in order to confirm uniform wall thickness around and along the billet within allowable tolerance for the component; 
 (g) checking the billet to identify any remaining curvature about the longitudinal axis of the bore; 
 (h) performing a further straightening operation on the billet to correct any curvature outside of allowable tolerance detected in step (g); 
 (i) performing a final machining operation in order to form any ports and upstands which are required in the component and to remove any other unwanted material from the exterior of the billet; and 
 (j) performing a fine honing operation on a longitudinal bore in order to reduce the wall thickness and a diameter of the bore to the final specified values. 
 
     
     
       2. The method according to  claim 1 , wherein the longitudinal bore is a blind bore. 
     
     
       3. The method according to  claim 1 , wherein the rough machining operation comprises a turning operation. 
     
     
       4. The method according to  claim 1 , wherein the rough machining operation includes forming a flange on the exterior surface of the billet at each axial position at which an upstand is required on a final work piece, each flange being sized to allow it to be machined in the third machining operation to form the required upstand associated with its position on the billet. 
     
     
       5. The method according to  claim 1 , wherein the first and second flanges are associated with opposing ends of the billet. 
     
     
       6. The method according to  claim 1 , wherein forming of the flanges and reduction in the size of the exterior surface of the billet in the rough machining operation is carried out in a single machining operation. 
     
     
       7. The method according to  claim 1 , wherein the longitudinal bore is formed by a boring operation. 
     
     
       8. The method according to  claim 1 , wherein the probing step comprising inserting a probe into the bore along the flange axis of the billet, and, at each axial position in which a measurement is to be taken, measuring the distance from the probe to the interior surface of the bore at different points around the bore. 
     
     
       9. The method according to  claim 8 , wherein the probe comprises a strain gauge which engages with the interior surface of the bore, changes in strain in the strain gauge being indicative of changes in the distance of the circumference of the bore from the flange axis. 
     
     
       10. The method according to  claim 8 , wherein the probing operation comprises mounting the billet on a bed which has first and second supports whose support surface complement the exterior surface of the first and second flanges respectively, the billet being supported on the bed by the first and second flanges being engaged respectively with the first and second supports such that the flange axis is parallel to the bed and aligned with the longitudinal axis of the probe which is mounted on the bed. 
     
     
       11. The method according to  claim 10 , wherein the billet is rotatable on said supports so as to allow the interior surface of the bore to be rotated around the probe whilst maintaining a flange axis aligned with the longitudinal axis of the probe. 
     
     
       12. The method according to  claim 11 , wherein the probing step comprises inserting the probe into the bore until is it as a first position along the billet at which a measurement is required, rotating the billet on the bed whilst monitoring the reading from the probe to record changes in the distance of the surface of the bore from the probe, and repeating for each additional measurement point required. 
     
     
       13. The method according to  claim 1 , wherein the straightening operation comprises deforming the billet in a press, and further includes machining the exterior surface of at least one of the first and second flanges in order to correct any eccentricity detected at the at least one of the first and second flanges after the straightening operation has corrected any eccentricity at the at least third point on the billet. 
     
     
       14. The method according to  claim 1 , wherein said further machining operation comprises a turning operation which reduces an outside diameter of the billet, excluding the flanges. 
     
     
       15. The method according to  claim 14 , wherein said further machining operation is followed by a second probing operation on the interior surface of the bore in order to check the concentricity of the interior surface about the flange axis; said second probing operation being carried out at said first point, said second point and at said at least third point. 
     
     
       16. The method according to  claim 15 , wherein said second probing operation is followed by a second straightening operation to correct any curvature in the billet outside of allowable tolerance measured during said second probing operation. 
     
     
       17. The method according to  claim 15 , wherein a still further machining operation is carried out after second probing operation and before step (f) in order to further reduce the outside diameter of the billet, away from the flanges, to the outside diameter specified for the component. 
     
     
       18. The method according to  claim 17 , wherein the amount of material removed from the billet during said still further machining operation is smaller than in any one of said preceding machining operations. 
     
     
       19. The method according to  claim 1 , wherein measuring the wall thickness of the bore comprises measuring the wall thickness from the outside of the billet at said at least two axial position, measurements at each axial position being take at least at three different points around the outer circumference of the billet. 
     
     
       20. The method according to  claim 1 , wherein said final machining operation comprises at least one of a milling operation to remove excess material from said flanges in order to form upstands which are required on the component, and a drilling operation to form any bores which are required to interconnect with the axial bore in the billet.